This invention relates generally to electroluminescent lamps and more particularly to an improved method and structure for making electrical connections to an electroluminescent lamp from only one side of the lamp.
Electroluminescent lamps are generally constructed as laminated or layered structures. Electroluminescent lamps function by application of an electrical potential to two conductive layers separated by an electroluminescent layer, which may comprise electroluminescent particles fixed in a resin binder.
Electroluminescent lamps have been modified to provide a lighted watch dial, as disclosed in U.S. Pat. No. 4,775,964 issued Oct. 4, 1988 to Alessio et al and assigned to the present assignee. While it is easy to make one of the electrical contacts to the back electrode comprising a conductive area on the underside of the electroluminescent watch dial, it is more difficult to make the other electrical contact to the front electrode, since this is a conductive layer which is embedded between other layers. Therefore it has been either necessary to omit part of the electroluminescent material to expose the front electrode, as shown in the aforesaid Alessio et al patent, or to provide a special overlap area extending beyond the normal periphery of the lamp.
An improved electroluminescent watch dial support and connector assembly is shown in the co-pending application of Thorgersen et al, Ser. No. 08/012,494 filed Feb. 2, 1993 now U.S. Pat. No. 5,265,071 issued Nov. 23, 1993 and assigned to the present assignee, employing special tabs extending beyond the dial periphery for making electrical contact. However it would be desirable to make electrical contact to both of the EL electrodes from any location on the back of the EL lamp without regard to the location of the lamp periphery.
It should be recognized that wherever electroluminescent material is missing, there is an objectionable dark spot on the lamp, since there are no electroluminescent particles to luminesce. In the case of an electroluminescent watch dial, it is preferable that the entire area used for observing the timekeeping numbers or other indicia be lighted without the presence of such a dark spot. However, there are some areas near the center of the watch dial in which a dark spot may be permitted without interfering with the aesthetic qualities of the timepiece. It would be desirable to provide a means for manufacturing an electroluminescent watch dial, in which the dark spot could be located wherever desired, and which also would permit electrical connection to both front and back electrode from any location on the rear of the electroluminescent watch dial.
Accordingly, one object of the present invention is to provide an improved electroluminescent lamp and method of making same, with electrical contacts on only one side of the lamp.
Another object of the invention is to provide an improved electroluminescent watch dial in which the electrical contacts and dark spot may be located at any desired location on the dial.